Telephone system



H. G. WEBSTER TELEPHONE SYSTEM 1 Filed Sept. 20, 1906 s Sheets-Sheet 1 Oct. 12 1926. 1 ,s02,731

H. G. WEBSTER f TELEPHONE SYSTEM Filed Sept. 20, 1906 3 Sheqts-Sheet 2 Oct- 12 1926.

H. G. WEBSTER TELEPHONE SYSTEM Filed. Sept. 20, 1906 3 Sheets-Shqet 3 WWW H16. Q/QJWATIZQ aw Patented a. 12, 1926.

UNITED STATES PATENT OFFICE):

HARRY G. WEBSTER, OF CHICAGO, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS, TO KELLOGG SWITCHBOARD & SUPPLY COMPANY, A CORPORATION OF ILLINOIS.

i TELEPHONE SYSTEM.

Application filed September 20, 1906. Serial No. 335,420.

The present invention relates to telephone exchange systems of the so-called auto matic type, in whichelectrically controlled switches are operated in response ,to current impulses controlled at a substation to connect the line ofa calling subscriber to any other desired line.

In systems of this class now in common use, the automatic mechanism at the central exchange is controlled through the operation of two relays, one of which is associated with each line limb. When it is desired to establish connection with otherlines, these relays are operated by grounding successively first one line limb and then the opposite line limb; and when connection is to be disestablished, the automatic mechanism is re turned to its normal position by grounding both line limbs simultaneously, thus operating both relays at the same time. One object of my invention is toprovide a system of the general character set forth in which the use of a ground or third conductor at the substation is unnecessary, and in which the impulses which control the automatic mechanismat the'exchange are transmitted over the talking limbs of the line exclusively. Further objects of the invention are to provide a system in which the impulses which operate the central mechanism may be transmitted when the central battery is in bridge of the line limbs, and one in which the central -mechanism is returned to its normal position byopening the circuit of the line limbs when the receiver is replaced at the conclusion of conversation. ,Another object of the invention is to provide an automatic system in which the controlling impulses may be transmitted over'a single wire and earth return, rather than by two wires and earth return, as in previous systems. My invention looks further to the simplification of the central mechanism and to the provision of an organization which shall be positive and reliable in operation and of decreased cost for construction and maintenance.

In accordance with my invention, I associatewith the circuitextendin from the central .oflice a primary relay w ichis responsive to both long and short interruptions of itsenergizing circuit, and a secondary relay which will not, respondto a. short or instantaneous [interruption but will reexchange. mary and secondary relays are operated by invention as applied the subscribers line spond toan interruption of definite duration. The substation is provided with switching mechanism, manually controlled, which will cause shortand long interruptions of the line circuit in theproper sequence. The automatic mechanism at the central office, by which connection is established with a desired line, is controlled by the successive operation of the two relays. In one form of my invention,-the mechamsm is restored to its normalcondition at the conclusion of conversation by the final de-ener ization ofthe secondary relay. In amodi ication of the invention, the line circuit includes a release relay and a high resistanceat the substation, the releaserelay being energized by current through the high resistance duringfthe sending of the controlling impulses. and operates, when the circuit through theline isentirely interrupted, to operate the restoring mechanism at the In this arrangement, the priinterruptions of a low resistance circuit in .shunt of the high resistance atthe substation. aspects of the invention The above and other features and willbe more fully understood by reference to the following. detailed description takenin connection with the. accompanying drawings, andthe scope of the invention will be particularly pointed outrin the appended claims. n

Referring. to the drawingaliig. 1 is a diagrammatic illustration of my invention as applied to systems .in which each subscribers line terminates in a so-called first selector switch which, when operated, selects and makes connection to a connector switch, which in turn selects and makes'connection to the'desired line. Fig. 2 is a diagrammatic illustration of a modification of my invention as applied to a similar structure the modification consisting in the use of a single wire andearth return for the line circuit; and in the employment of a high resistance at the substation and a special release relay at the first selector. Fig. 3 illustrates the to a system in wh ch terminates directly in a connector? switch, this embodiment of the invention. being therefore limited toexchangesof ,suc-h size that themultiplecontacts of all lines: may be present in the connector switch. As in Fig. 2,, but onewire is used between the central office and the substation. Fig. 4 is a mechanical diagram of the substation equipment of Fig. l illustrating dial mechanism for actuating the calling device contacts. Similar characters refer to corresponding parts in the several figures.

Referring to Fig. 1, a substation A is in dicated as extending in two limbs 2 and 3 to a central oil ice D. The usual hell I; and condenser are included in normal bridge of the line limbs, and a receiver 1 and transmitter are in an alternate bridge which is completed by the elevation of the switch-hook h. 1 am not limited, however, to the particular arrangement of these devices indicated by the diagram, as it is obvious that other well known arrangements may be equally well employed. The substation is also provided with means whereby the subscriber in mak ing a call can cause the low resistance circuit including the transmitter to be interrupted momentarily any required number of times; and whereby any number of short interruptions will be automatically succeeded by an interruption of relatively long duration. Substation circuit changing mechanism of this general character is well known and is diagrammatically indicated by the switches S and 1. The selector switch A is associated with the line A and is provided with a moving member or wipershaft S carrying moving contacts or wipers 33, 34: and 35. These wipers are associated with fixed or bank contacts 36, 37 and 33 which constitute the terminals of circuits leading to a connector switch A These bank contacts are associated with other bank contacts of similar connector switches, so arranged in groups that, by the movement of the member S, the wipers may be moved in one direction until opposite any particular group of bank contacts, and then moved in a direction at an angle to the first motion whereby the wipers will successively engage the several contacts in the group. The wipers 34: and 35 are so arranged that, in passing over contacts 37 and 38 and other similar contacts, they will move out of en gagement with one contact before engaging the next; while Wiper 33 is so constructed that, in passing over contact 36 and other similar contacts, it will engage one contact before disengaging another. The wipers are normally out of engagement with the contacts. The first motion of the moving memher or shaft S is effected by the vertical magnet VM by means of step-by-step mechanism, operating to advance the shaft one step in a linear or vertical direction each time the magnet VM is energized, and it is to be understood that two such steps are required to bring the wipers opposite the first group of bank contacts. The angular motion of the shaft is secured by means of the angular magnet AM by similar stepby-step positions.

mechanism, the arrangement being such that the wipers will engage the first contacts of a group the first time the magnet AM is energized, and another set of contacts with each succeeding energization. Associated with the shaft S is a switch V0. This switch is so arranged that at the first vertical step of the shaft, the contact spring 32 will be shifted from its normal to its alternate contact, and contact springs 29 and 31 will be shifted to engage contact spring 30. At the second step of the shaft, contact spring 31 disengages spring 29, and this position of all springs is then maintained during subsequent motions of the shaft. The shaft is returned to its normal position by suitable mechanism actuated when the re lease magnet RM is energized. This mechanism, as well as that controlled by magnets AM and VM for securing the vertical and angular motions of the shaft, is omitted from the diagram for the sake of simplicity, but such mechanism is well known and may be of any desired character, it being understood that it is actuated in each case at the time the respective magnets are energized, rather than at the time they are de-energized. The connector switch is provided with a similar shaft S controlled by vertical and angular magnets VM and AM and has a switch V0 having contacts corresponding to contacts 29, 30 and 31, which are operated in a similar manner. Its relation to the corresponding bank contacts 72, 73 and 74 is such that the wipers will not be brought opposite a group of contacts un til the second step is made, but differs from that of the selector switch in that wiper 69 disengages one bank contact 72 before engaging another; and in that the wipers will not engage the first contacts of the group until the second step in the angular direction. A switch A0 is associated with the shaft, which will close a contact at the first angular step of the wipers and interrupt the same contact at the second angular step, and this contact is closed and interrupted regardless of the number of vertical steps which the shaft may have made. The shaft and wipers are likewise restored to their normal positions when the release magnet RM is energized. The bank contacts of this switch constitute the multiple terminals of other telephone lines. The magnet AM of the selector switch is energized preferably by a pulsating current from the battery B through the interrupter I, and its relation to the secondary magnet SM is such that at each pulsation by which the magnet AM is energized, the armatures 23 and 24 of magnet SM will be brought to their attracted This action may be secured by any suitable mechanical or electrical arrangement and the illustration is diagrammatic only. The magnet SM controls, by its armature 24, the moving member or'switch shaft K. When armature 24 is attracted, the pawl 25 will engage atooth ofthe mem ber K; and when the magnet is subseq y llgiZed, the retraction of" mature 24 will advance the member K one step, when it will then be retaining pawl 26; and the switch arms or levers 14, 17 and 20 are thus moved to their differentpositions. At the time of release, the energization' of release magnet RM causes extension 27, of the armature'QS; 'to

engage pawls 25 and 26, throwing them out of engagement with member K, which is then returned to itsv normal position by the spring is. 1

The illustration of the member K and its associated mechanism is diagrammatic only and 'it will be understood arrangement may be employed wherebythe switch arms14, 17 and 20 are advanced one stepat each energization and subsequent'deenergization oi magnet SM, and by which the arms are restored to their normal positions through the energization of magnet RM. The connector switch A is provided with a similar switch arm K, controlled y;

relays SR and 44, andrestored by the energization of the release magnet RM. This arrangement is such that the advance of the levers 45, 49, 53 and 57 is secured by the operation of either relay.

Considering now the operation" of the mechanism when the subscriber A desires connection; the removal of the receiver 7' closes circuit through limbs 2 and 3, result ing in a current flow over the circuit from the active terminal of battery B, through the winding of the primary relay PR, thence through the normal contact and armature contact? of the cut-off relay CR, thence thiiougl'i limb 3, the switches P S, the receiver and transmitter, limb .2 and to the return side of the battery through the impedance 9. The primary relay PR is a relay which will release its armature in response to long orshort interruptions of the circuit of the line limbs. As it is now energized, circuit is closed at armature contact 11, throughswitch lever 14, contact 15 and magnet V M, causing the shaft S to move one step in the linear or vertical direction. Likewise, circuit is closed at armature contact 10, through the secondary relay SR to the battery B, energizing the secondary relay SR. The secondary relay is a slow-acting relay and its armature will only be retracted in response to interruptions of relatively long duration. It is indicated as being vidcd with a copper. shell around its iron core to secure this slow release of its armaf true, but it is obvious'that other methods may be employed for securing this action. As it is now energized, armaturecontact 12 completes a circuit for the secondary magnet held by the that any suitable pro- SM, which may be traced fromthe'upper terminal of battery B,ithroiigh' the winding ofinagii'et SM, contact 12 of relay SR and to the return'side of the'batte'ry through contact' l7 andswitch lever 17. This ener g'izes magnet SM, andthe attraction of arinature 24 causesthe pawl 25 to engage the first tooth of'the member K. noted that limbs'2 and 3 of the line are norinally'conne'cted to wipersj35 and 34 respectively ofth'eshaft S; p The energization'of magnet SM disconnects these wipers near the line limbs at contacts samura To return now to the firstfsteptakemby the" shaft S" in response"to the initial"energifz'ation of magnet VM;this first step causes the" operationof the switch VO. Multiple or bank contacts of line A are shown at 4, 5 and 6. These are to be understood as 'bankeoir, tacts located upon a connector switch and corresponding to the'contacts'72, 73 and '74 at the right of thed'rawing and constitute the multiple'cont'acts of the line, whereby other lines may connect thereto. These'contacts are multiply conne'ctedto' similar con tacts on other'connectorswitches, such mul; tiple contacts being indicated at 4*, 5 andG Contacts 5 and 6 are talking terminals of the line, and contact 4 is the terminal of a local or private circuit. As will be"subsequently pointed out, the contact 4 of'all lines which are in use will have a low resistance connection to the return "Side of the battery '15; while,f'if the line be idle, this contact is con nected to the active side of the battery throughthe winding of the cut-ofi' relay CR. I This normal connection may be traced from theupperlterniinal 'of'the battery B through the winding of relay CR, thence, through contact 16 and' lever come through sp'ring'32 of the'switchVO whenfin its normal position, When the first step of theswitch was made; spring '32 disengages its normal contactand engages its alternate contact, thus discos nesting the bank contact 4 from' the cut-off relay andfrom the wiperBZ-B and connectingit' to the return side ofthe battery as indicated. Likewise the first step of the switch' has caused springs 29 and to the return" side of the battery at contact 3 Ilnow', instead of operating the interrupting switchesS and P at the substation, the subscriber should replace his telephone. the shaft S and its wipers would be returned to their normal positionas iollows The in terruption ofthe'circuit through limbs 2 and 3 would tie-energize relay PR {the retraction of contact 10 would deenergize relay SR; the retraction of contact 12 of relay SR would de energize magnetSM'; andthe re traction ofits armature 24 would move the member K one step, except forlthe retraction of contact; 13of relaySR. The retraction of thiscont'act closescircuit through the re It will be and thence to the contact 4."

31 to be connected 3 lease magnet RM however, this circuit being traced from the upper terminal of battery 13 through the winding of magnet RM, contact 13, springs 31, 29 and 30 of the switch V0, to the return side of the battery. The attraction of armature 28 closes a locking circuit for the magnet RM through springs 29 and 30; the armature extension 27 engages the pawls 25 and 26, thus throwing them out of engagement with the member K and preventing its forward motion; and mechanism associated with the magnet EM causes the shaft S to return to its normal position and interrupt the locking circuit of magnet BM at contact springs 29 and 30.

Assume now that instead of immediately replacing his receiver, subscriber A proceeds with his call. The selector switch is then in a condition in which relays PR and SR- are energized, magnets VM. and Slit are energized, and the shaft S las taken one step in a vertical direction. The subscriber now manipulates his interrupting mechanism SP so as to give a number oi short interruptions to the circuit of the line limbs, corresponding to the group oi bani: contactscontaining the terminals of the connector switch which is to be selected, followed by a single long interruption. At each short interruption, the armature of relay PR is released. As contact 11 is sub sequcntly attracted each time, the magnet VM is en rgized, causing the shaft to take one step in the vertical direction; and spring 31 or the switch VO disengages spring 29 after the first short interruption. At each retraction of contact 10, the circuit oi relay SR is interrupted, but the interruptions are of too short duration to allow the relay magnet to become ale-energized and its armature therefore remains attracted and maintains the energizing circuit of magnet Shit. lVhen the long interruption takes place however, the circuit ot relay SR is interrupted at contact for a su'liicient length of time to allow the retraction of its armature. The retraction of contact 13 does not now energize the release magnet RM for the reason that the circuit previously closed through contact 13 is now interrupted at spring 31. The retraction of contact 12 de-energizes the secondary magnet SM and its armature drops back, causing the advance of the member I; one step. This motion causes switch lever l t to in terrupt the circuit of magnet VM; causes switch lever to disconnect the wiper 33 from the cut-oil relay GB at contact 16, and to connect the wiper to the winding of magnet SM at contact 21; and the motion oif lever 17 disconnects contact 12 at contact 17 and connects the angular driving magnet AM to the return side of the battery at contact 18. The magnet AM will now be energized the first time circuit is closed through the interrupter I. When so energized, the armature oi"? magnet SM is brought into its attract-ed or alternate position disconnecting wipers 3 1 and 35, and he shaft and wipers are caused to take one step in the angular direction, bringing the wipers into engagement with the first set of bank contacts in the group. It' the connector switch, associated with these first contacts, be busy, the contact 36 will be connected directly to ground at spring '76, and a circuit is thus closed from the upper terminal of battery 13, through the winding of magnet SM, contact 21, lever 20, wiper 33, contact 36 and spring 76 to the return side of the battery, thus, maintaining the armature of magnet SM in its attracted po sition. The banlr contacts 36, 37 and 38 are contacts on the selector switch similar to contacts 4, 5 and 6 on the connector switches, and have multiple contacts 36, 3"! and 38 on other selector switches. At the next pulsation of current through interrupter I, magnet AM is again energized, causing the shaft S to take another angular step, and this motion will continue, step by step,as long as the wiper 33 passes over grounded rontacts. its construction is such that it will remain in engagement with a contact 36 until after it engages the next succeeding contact, and the energizing circuit tor magnet SM is thus maintained until a contact is engaged which is not con nected to the return side of the battery. hen this occurs, the circuit of magnet SM is interrupted; its armature drops back, connecting the line limbs to the wipers and 35; and the driving pawl causes the member I: to take a second step, shitting the switch levers 14, 17 and 20. This operation of lever 17 interrupts the circuit of magnet AM, preventing the further angular motion of the wiper shaft, and connects contact 13 to the return side of the battery at contact 19. The operation of lever 20 likewise disconnects the secondary magnet Sid and connects the wiper 33 to the winding of the secondary relay Sid. Circuit has meanwhile been closed througl the line limbs by the re-engagcment of the contacts indicated at S after the long interruption, and a new circuit condition results. Relay PR- is now energized, but the circuit of armature contact ll stands open at lever 14:; wiper and relay SR are connected to the return side of the battery at armature contact 10, and armature contact 13 is thus maintained attracted, preventing at this time the operation of the release magnet RM; while the circuit of magnet SM is now interrupted at contact 21 and the magnet SM thus remains inert, leaving the wipers 34 and connected to the line limbs.

A new circuit may now be traced from the upper terminal of the battery-through the wzndingof the primary relay PRQo f theeonnector switch, contact 37, wiper 34, armature contact 23, armature contact 7, limbs 3 and 2 to the return sideof the battery through the impedance 9. The relay PR is thus energized at the instant the. connector switch A is selected. The attraction of armature contact completes a circuit for the vertical magnet VM, causingthe shaft S to take one vertical step. The actuation of armature contact 39 closes the circuit of the secondary relay SR; and the energization of this relay interrupts the circuit through the release magnet RM marmature contact 41, which would otherwise be closed at springs 61, 62 and 63 of switch V()' at the first step of the wiper shaft S The attraction of armature 42 0f relay SR causes the driving pawl 77 to engage the first tooth of the moving member K. If now, instead of sending the proper impulses to cause the desired line to be selected, the subscriber should replace his receiver, the

* apparatus of the two switches would return to its normal position for the follow 111g reasons: The de-e'nergi-zatlon of relay PR would interrupt the circuit of relay SR, and the retract-ion of contact 11 would complete a circuit for the release magnet RM similar to that described for magnet RM of the selector switch, causing the wiper shaft to returnto its normal position and preventing the retraction of armature 42 from causing a forward motion of the member K. Relay SR of the selector switch has at this time been energized over the circuit closed at armature contact 10 of relay PR and also closed through contact 22, lever 20,

wiper 33, contact 36, and contact 76 controlled by the wiper shaft S This latter contact was completed at theffirst vertical step of the shaft. This shaft has-now returned to its normal position and relay PR is de-energized. The circuit of relay SR is thus interrupted andthe retraction of armature 13 energizes magnet RM and operates the restoring mechanism as previously described. Thedisengagement of the pawls I s 25 and 26 allows the switch levers 14, 17-and 20 to be returned to the normal position shown in the diagram. Assuming that the subscriber does not replace his receiver but proceeds to send the necessary impulses to cause the connector switch to pick the'line gesired, he thenmanipulates his apparatus 'P ruptions corresponding-to the group of bank contacts containing the-contacts ofthede sired line, and followsfthese short'interruptions by a's'ingle longinterruption. Atth'e first interruption, the shaft S takes itss'ec-j 0nd vertical" step, bringing its wipers 69, andZl opposite: the first group of contacts, 'thismotion being the in so as to give a number ofshort interterrupting and closing of the circuit-through vertical magnet VM at armature contact 40, and these steps are continued until the desired group 13 reached. The correspondin interru J-tions .at armaturecontaet 39 of the circuit through relay SR, are of too short duration to allow the armature of the, latter relay to be retracted. Relay SR of tact 41 does notn'ow complete the release.

circuit of "RM forthe reason that spring 61 has moved out of engagement with spring 62 at the second vertical step of fthe'shaft'; but the retraction of armature QQca'usesthe member K" to advance one step. The motion of lever interrupts the 'circuitiof magnet VM and brings the angular driving magnet AM under control of the armature of relay PR. Relay PR is nowenen gized as circuit has been closed at the sub station, after the long interruption; completes the circuit of relay SB at contact 39; and energizes magnet AM through the circuit completed at armature cOntactO, thus causing the wiper shaft to take one step in the angular directiom It will be remembered that the wipers of the connector switch do not engage the contacts until the second angular step. At this first step, the movement of switch AO brings magnet RM again under control of armature con tact 41 of relay SR, by the circuit closed at spring 83 of the switch AO. If now the subscriber replace his telephone before sending the final set of impulses to select the particular line he desires, the retraction of contact 41 of relay SR completes the release circuit through magnet RM and the wiper shaft of the connector switch is re stored to its normal. position; and at the end of its movement, interrupts the circuit of relay SE at contact 76 thus causing the selector switch to return to its normal position, all as previously described. Assum ing that the subscriber proceed with'his call, he nowgives a number of short interruptions corresponding to the'position in the group of'bank contacts, of the contact of the line he desires to connect with, following these short interruptions by a long interru tion. a V a a I f'the desired line he busy,rthe private or local contact 72 will have a low resistance connection to the return side of the battery; either that described for contact 4 through spring 32, if the line be busy through having initiated a call; or another low resist a e' conn i n obe subsequently described;

if it be busy through having been already called. At each short interruption, the attraction of armature 4O energizes magnet AM, causing the switch to take one angular step, and the circuit through spring 83 is interrupted at the second step as previously pointed out. The wipers 69, and 71 pass over the corresponding contacts of the various lines in the group during these angular steps; they are each so arranged that they disengage one set of contacts before engaging a second set, and are open at this time at contact points 49, and 68 respectively; anl thus no interference will occur with those lines which may be in conversation. After the wipers have been brought into engagement with the contacts of the desired line, the long interruption causes the de-energizati on of relay SE. The retraction of contact 41 does nothing at this time, but the retraction of armature 42 causes the member K to take a second step. The corresponding movement of lever 45 interrupts the circuit of magnet AM, preventing the further motion of the wipers; the motion of lever 53 extends limb 3 of the line A to the condenser c; and relay 65 is connected to wiper 69 by the engagement of lever 49 with contact 51. If the line be busy, contact 72 will be connected to earth and relay 65 will not be energized. The subscriber will then get the busy indication, consisting of the ordinary buzz" produced by current through the interrupter I and the windings of the busy back induction coil C. The circuit for this current may be traced from the coil C, through condenser 0, contact 75, contact 82, condens r 0, contact point 55, lever 53, bank contact 37, wiper 34, contact 23, contact 7, limbs 32 and impedance 9 to the ground or office return. He will thereupon replace his re ceiver, again de-energizing relays PR and SR, which had been energized at the conclusion of the last long interruption. The retraction of armature 42 now causes the member K to take a final step, completing a release circuit for magnet RM through contact 60 and lever 57. The energization of this magnet again completes the locking circuit for itself, through armature contact and spring 62 and 63; the engagement of extension 7 9 of armature contact 80 with pawls 77 and 7 8 allows levers 45, 49, 53 and 57 to return to their normal position; and other mechan sm associated with the magnet restores the wiper shaft to its normal position, thus interrupting the locking circuit at spring 62 and releasing the selector switch at contact 76, as previously described. If the des red line be idle, contact 72 is connected to battery through the winding of the out off relay. This connection is shown for line A from the upper terminal of battery B, through the winding of relay CR, contact 16, switch lever 20, contact 32 of switch V0, and

multiple contact 4. Current will therefore flow, after the last long interruption, froi'n contact 72, through wiper 69, lever 49, contact 51 and the winding of relay 65 to the return side of the battery, energizing relay 65 and actuating its contacts. Belay GB of the called line is also energized and the actu ation of its contacts 78 disconnects the line limbs from its relay PR and connects them to bank contacts 7 3 and 74. As contact 66 of relay 65 is actuated, it closes a short circuit about a portion of the relay winding, sufficient of the winding being left in circuit, however, to maintain the attraction of the relay armature. If, after this relay has been energized, contact 72 should be engaged by the wiper 69 of another connector switch, the relay 65 of the other switch would not receive suliicient current to cause the attraction of its armature by reason of the shunt through relay 65 of the switch A and it is this means by which the low resistance earth connection to contact 72, previously referred to, is secured when the line is busy by reason of its having been selected by a calling subscriber. The actua tion of contact 75 disconnects the busy back arrangement C and completes the talking circuit of limb 3 to wiper 70 and contact 73, which contact corresponds to contact 5 of line A. The actuation of contact 68 completes the circuit of limb 2 to wiper 7] and contact 74 which corresponds to contact 6 of line A. The actuation of contact 67 completes a circuit for relay 64, which may be traced from the upper terminal of battery B, through armature contact 43 of relay 44. the winding of relay 64, armature contact 67, and through interrupter T to the return side of the battery; and relay 64-. is ener ized each time circuit is closed at the intern hen relay 64 is inert, the winding of relay 44 is included in circuit with battery B, and with the subscribers line corresponding to contacts 7 3-74 which now stands open at the condenser and bell. At each energizaticn of relay 64, the actuation of contacts 81 and 82 includes the signal ng generator G- in circuit with the line limbs, thus ringing the bell of the desired line. After the subscriber removes his receiver, relay 44 energized at the first subsequent de-cnergization of relay 64, over the circuit through armature contact 82, armature contact 75, wiper 70, the line limbs and impedance 9 of the called line. The attraction of armature contact 43 interrupts the circuit of relay 64, thus preventing a subsequent application of ringing current, and the two sub scribers are in condition for conversation, current being supplied to the transmitter of line A through the windings of relays PR and PR and the impedance 9; and to the called line through the winding of relay 44 and its impedance 9. The talking circuit is hit) lit)

iii.

completed from the lineli-Inb 3 tcthe correspondingline li n-b 'of the called li-ne, through contacts 7--23, wiper 34, contact- 37, lever 53, contact 55, condenser contacts 825-75, wiper 70 and contact 73, and from line limb 2 to the corresponding limb of the called line, through contacts 24;90, wiper 35, contact 38, condenser 0 contacts Sl-68, wiper 71 and contact 74.-

Armature 98 0f relay 44 is at this time attracted and the pawl '78 has engaged the next tooth in the moving member K. If the called subscriber replaces his receiver before subscriber A, his line will be disconnected and the wiper shaft may return to its normal position and then make a first vertical step. This operation is secured as follows: When relay 44 isde-energized by the interruption of its circuit at the substation of the called subscriber, armature 98'is retracted, moving the member K and the switch levers to the last position. The disengagement of lever 49 and contact 51 interrupts the circuit of relay 65 and its contacts return to normal, thus disconnecting the wipers 70 and 71 and the relay .64. The disen agement of lever 53- and contact 55 interrupts the circuit of limb 3 of the line A, preventing thatsubscriber from getting a busy indication at this time, and the engagement of lever 57 with contact 60 completes the circuit of magnet RM. The ener gization of this magnet completes the lockingcircuit for'its'winding through armature SOand springs 62 -633 of switch V0. The extension 79 of the armature throws the pawls 7'7 and? 8 out of engagement with K, allowing the levers 15, 4:9, 53 and 57 to be returned .to .their normal positions by the spring'k. At the same time, the mechanical connection between magnet RM and shaft S has caused the shaft to return to its normal position, interrupting the circuit through the winding of RM at spring 62 as it comes to rest. A circuit, due to the energization of relay PR at this time by current through line A, was closed for magnet VM when lever i5 engaged contact {$7. As soon, therefore, as magnet RM is de-ener gize'd by the interruption at spring 62, the shaft- S will be given the single vertical step by the energizationof magnet VMQ If subscriber'A now replaces his receiver, both the selector switch A and connector switch A will be restored totheirnormal positions, in that manner described under the assumption that the subscriber A replaced his'receiver after making the first set of'interruptions.

In restoring the connector due tothe replacing of the called subscribers' receiver as just referred to, should the switch-arm 45 return to normal before the wiper shaft,

m not Vic." will a 'ain b'e'ener' ized'. ,Th s 4 b v k 1 will causeits awl to engage and revent restoration-o f the shaft from-its vertical adjustment, until the calling subscriber replaces his receiver and-causes de-energization of relay PR, thus interrupting the circuit th-ru VM whereby it de-energizes allowing the shaftto restore.

Returning now to the condition when the subscribers are talking, if subscriber A re place his receiver first, both switches will be immediately disconnected as follows: is has been already pointed out, circuit was closed through relay SR at the end of the final long interruption at the substation. A. Armature 41 2 is therefore in its attracted position, and armature 98 was attracted when the called subscriber answered. The release of either arn'iature will throw the switch levers to their final positions. lVhen subscriber A replaces his receiver, circuit is interrupted through relays PR and PR and their armatures drop back. The energization of relay SR is at this timemaintained by the circuit through contact 22, lever 20, wiper 33 and spring 76. The circuit through magnet SR is, however, now interrupted by the retraction of ar1natu're contact 39. Armature 412 is therefore retracted, causing the interruption of the circuit through relay 65 and by the'retraction of the armature of'relay 65 interrupting the circuit through relay l-4i. The release circuit through magnet RM is established as before at contact60 and the member K and the shaft S return to their normal-positions; When the circuit through relay SR is interrupted-at spring 76 by therestoration of the shaft S the retraction'ot' armature contact 13 likewise closes the release circuit through magnet BM, thus restoring the shaft S as previously described. As relay PR is at this time ole-energized, the circuit ofmagnet V M is not closed and the shaft S remains in its normal position. The apparatus is, now ready for another connection. The relation between magnet AM and magnet RM is such that when magnet RM is energized at the time of release, the various pawls are moved out of operating position and magnet AM- will therefore not operate to prevent the restoration of the shaft- S as lever 17 passes contact 18' when returning to its normal position; and a simi' lar relation exists between magi'iet AM and magnet RM.

The structure of Fig. 2 differs from that of Fig. 1 in the arrangement at thesubs'tation' A; and in the arrangement at the central Once, whereby a primary relay PR and a' secondaryrelay" SR arenorinally included directly in circuit with the line; and a release relay RR isalso in circuit with the line. ,In this structure, instead of connect in}; the-subscribers and the" central oflice with" two metallic line'linibs, but o wire to-- the substationiseniployed and the return llli) circuit is secured by the earth connection 9. A relatively high resistance R is provided at the substation in that portion of the circuit closed by the elevation of the switch hook 71., and this resistance is normally in multiple with a low resistance circuit including the contacts of the interrupting switches P and S. The relay RE is sufliciently sensitive to be energized by current either through the low resistance path or through the resistance R. Relays P1. and SR will attract their armatures when energized by current through that portion of the circuit including switches P and S; but when this circuit is interrupted, armature contact 83 will be released by either a short or long interruption, and armature contact 12 of relay {R will be released in response only to a long interruption. The connector switch A is similar in its operation to the connector switch A the only difference in the structure being the omission from A of contacts 74, 74, etc., wiper 71, armature contact 68, armature contact 81, condenser 0 and their connecting wires, these being the parts which, in switch A controls the talking current of limb 2 and the corresponding limb of the circuit to the called subscriber. Likewise, the impedance 9, limb 2, armature contact 8, contact 2 1, contact 90, wiper 35, contact 38 and their connecting wires, which in selector switch A were provided for controlling the talking circuit of the limb 2, are omitted from selector switch A hen subscriber A removes his receiver to start a call, current will flow from the upper terminal of battery B through relay RR and through relays SR and PR contact and lever 14, and thence through limb 1, switch-hook h, receiver a" and transmitter Z? to ground g through the contacts of switches P and S. The energization of rela SR completes a circuit of magnet SM at armature contact 12, causing the attraction Of armature 24, which interrupts the circuit through wiper 34: and brings pawl into engagement with a tooth of the member K. The energization of relay PR closes a circuit for the vertical magnet VM at armature contact 83. The energization of this magnet causes the wiper shaft S to take one step in its vertical direction. This step operates switch V0 bringing spring 29 into engagement with its contact and shifting spring 32 from its normal to its alternate contact. This operation of spring 32 disconnects the multiple contacts H from the wiper 33 and cut-oil. relay CR and connects the multiple contacts directly to earth, thus providing the condition necessary to prevent the selection of this line by another calling subscriber.

It, now. the subscriber A replace his receiver without operating switches P and S, all three relays will be tie-energized, and the retraction of armature contact 84 of relay F73. will complete a circuit for release magnet Eli/1 through spring 29. Armature 2-lof relay SM is simultaneously released. The attr ction of armature 2S interrupts the circuit of wiper 3 1, and the armature extension 27 throws pawls 25 and 26 out of engagement with K thus preventing the advance oi the lovers 14-, 17 and 20 through the retraction of armature 2%. If, instead of replacii'ig his receiver immediately, the subscriber operates his switches P and S to make definite number of short interruptions followed by a single long interruption, the switch will select and make connection to those contacts 86 and 37 leading to an idle connector witch, as occurred in the structure of Fig. 1. When circuit is closed after each short interruption, the engage ment of armature contact 83 with its contact energizes magnet VM causing the shaft to move one step in the vertical direction. W hen armature contact 12 of relay released at the long interruption, the consequent de-encrgization 01" magnet SM allows the retraction of armature 24;, thus shifting levers 14, 17 and 20 to their second position. The movement of the lever 14. interrupts the circuit through relays SR and PR The movement of lever 20 disconnects wiper 3 from cut-oft relay CR and connects it to the winding of magnet Sit l and the engagement of lever 17 with contact 18 completes the circuit through interrupter T and magnet AM? The relation between magnet Ali and magnet RM is similar to that in switch 11., whereby magnet AM will not interfere with the restoration of shaft S when magnet RM? is energized. When circuit is closed through magnet Ali i at interrupter T, armature 2st of magnet Sh is thus brought into its attracted position and the wiper shaft S is given one step in a direction at an angle to its first motion, causing wipers and 3a to engage contacts and 37 respectively. As long as wiper 33 engages contacts 36 of busy lines, the consequent energization of magnet 3M maintains the armature in its attracted position and the wiper continues its travel. 11611 an ungrounded contact 36 is engaged, the circuit through magnet Fillil is interrupted and the retraction of armature 2d throws the levers 1a, 17 and 20 to their third position, interrupting the circuit of magnet AM at lever 17 and preventing a further motion of the wipers. As lever 20 disengages contact 21, the circuit of magnet St? is interrupted, thus preventing its subsequent energization when wiper 33 and contact 36 are connected to ground at spring 76 by the operation of the connector switch A When armature 2 L closes circuit at the back contact, a circuit is then completed for the connector switch A which may be traced from the SR is the c-ircuit has now been closed at the end' of the long interruption, relay PR is energized and shaft S makes an initial vertical step in the same manner and with the same results as did the corresponding shaft S in switch A". If the subscriber A were now to replace his receiver, the de-energization of relay PR would restore the connector switch A to its normal position; and the de-euergization of relay RR would restore the selector switch A to normal. The structure of this figure, therefore, differs from that of Fig. 1 in that the restoration of the selector switch is not dependent upon the connector switch interrupting the circuit throughv spring 76. An obvious modification to secure the busy condition of contact 36 would be the omission of spring '76, and the connection of contact 22 to earth as indicated at 23. If, instead of replacing his receiver, subscriber A now makes the interruption necessary to select the desired line, the switch A will operate in the same man nor was described for connector switch A At the conclusion of conversation, if the called subscriber replace his receiver first, his line will be disconnected and the switch A operate as did switch A the shaft- S being returned to normal and then taking the initial vertical step, and both switches would be restored when subscriber'A replaced his. receiver. If, at theconclusion of conversation, subscriber A be the first to replace his telephone, the; consequent deenergization of relay PR will release switch A and the de-energization' of relay RR will release switch A.

Fig. 3 is a diagrannnatic illustration of a structure different from that of Fig. 1 in having butone-wire between the central office and the substation Alf and in the absence of a selector switch, the switch A being a connector switch directly associated with the subscribers line, and operating to establish connection directly with the line of a desired subscriber, rather than through an intermediate link. The-construction of switch A is similar tothat of switch A of Fig. 2, and operates in a similar lnanner. When the subscriber removes his receiver, relay PR is energized, causing the energization of relay SR and the energization of magnet VM, whereby'the shaft S takes the initial vertical step. If the subscriber then immediately replace his receivelgthe switch is restored by the circuit initially completed at contact alfthro'ugh magnet RM? If, instead of immediately replacing his receiver, he operate the interrupting switches S and P, the short interruptions cause the wipers 69 and to be brought opposite the group of contacts in which the contacts of the desired line are located; and the de-energization of relay 6R at the long interruption shifts the levers associated with. K to their second position. If at'this time the subscriber replace his receiver, circuit will again be closed through the release magnet, RM at contact 41 and spring 83 of the switch A0 which is at this time in engagement with its contact, by reason of the shaft having made one step in its angular direction when circuit was closed at the end of the long interruption. Likewise, the initial vertical step of the shaft S caused spring 76 to move from its normal contact to'its alternate contact, thus disconnecting multiple contacts 4- 15 from the cutoff relay and wiper, and connecting them di-j rectly to ground. .If, instead of replacing his receiver, the subscriber cause the necessary interruptions to select the desired line,

the short interruptions will cause magnet AM to give shaft S the necessary number of steps to bring wipers 69- 70 mentwith the contacts 72-73 of the desired line. If the linev be busy, the low resistanceearth. connection will then be present for contact 72, relay 65'will not be energized, and the busy condition will be indicated to the subscriber by current from the busy back arrangement C through the condenser 0. If the line be idle, current will flow through the cut-off relay CR contact 52 and lever 49, spring 76 and contact 72 of the desired line, corresponding to similar connections of line A; thence through wiper 69 of switch A lever 49, contact 51 and relay 65, ener-. gizing both relays. The operation of the cut-off relay disconnects the desired line' from 'its relay PR thus preventing the operation of the switch of that line when the subscriber answers or when ringingcurrent is applied. The energization of relay 65 connects the line limb through contact to armature contact :82 of relay 64. The operation of armature contact 66 completes the shunt circuit of a portion of the relay winding, thus preventing the operation of a relay 65 of another calling line, should it be brought into multiple therewith by another subscriber attempting to make connection with the same desired line. The operation of armature contact 67 completes the circuit of frelay 64 through interrupter I Each time circuit is closed through the interrupter I", the operation of armature contact 82 connects the ringing generator G to the limb of the desired line, thus actuating the signal of that line. When'the line is answered, the first subsequent engagement of armature contact 82 with its normal contact cominto engagethe initial vertical step.

pletes the circuit of relay 4L4, thus interrupting the circuit of relay (it at armature contact i3 and bringing; armature 98 into its attracted position, whereby pawl 78 engages the tooth in member K. The two subscribers are now nnected tor conversation.

It the called subscriber first replaces his receiver; the retraction of armature 98 complctes the restoring circuit at lever 57 and contact (30; the sh aft 5" is restored to its normal position as are switch levers 4E5, 49 53 and 57; and then by reason 01 the continued energization of relay PR the energization ot' magnet VM' causes the shaft S to make It, now, subscriber A replace his receiver, the de-energization of relay PR causes the restoration of the shaft as was descriliied in the case where the subscriber immediatelv replaced his receiver without operating the switches S and P. If, at the conclusion of conversation subscriber A first replace his receiver the consequent retraction of armature 42 causes the switch mechanism to be restored and rest in its nor end position without the succeedingvertical step of shaft S.

it. will be seen by the foregoing description that in each structure the series of short interruptions causes the switch mechanism to bring moving contacts. associated with the militia line, into association with a desired group of tixed contacts; and that the lone interruption produces a secondary switching operation of the central mechanism. This secondary switching operation in the struc tures of Figs. 1 and 2 results in automatically associating the line ot the milling subscriber with the first idle. connector switch in the predetermined group. In the structure of Fig.1. 3. the secondary operation places the mechanism in condition whereby the desired contacts in the selected group may be: subsequently engaged. In the structures of Figs. 1. and 2, the second set of short interruptions causes the connector switch mechanism to associate the line with the group oi contacts in which the contacts of the desired line are located; and as in the structure of Fig. 3, the longinterruption causes a secondary switching operation whereby the switch may be subsequently controlled to bring; the wipers into engagement with the contacts of the particular line desired. The final set of short interruptions selects the desired line, and the final long interruption causes a secondary switching operation whereby" connection is established with the desired line and signaling; current applied thereto; or whereby the calling subscriber is given a busy indication if the line be already connected. In each structure, if the calling subscriber replace his receiver imniediately after a long interruption, the re snltin g1 interruption to the circuit causes the restoration of the switches to their-normal positions. If, after connection has been established, the calling subscriber replace his receiver, the switches will be restored to their normal positions; and it the called subscriber replace his receiver at any time after connection has been established the connector switch which has connected to his line, will be restored to its normal position; and it at that time the circuit be closed through the line of the calling sultiscriber, the connector switch will make the initial step. 'l he mechanism, diagrammatically indicated by the switches S and P, may be 0t any desired character whereby the subscriber may make any desired number 0t short interruptions to be followed by a single long interruption in each case. Mechanism of this character is in common use. in l, I have shown a dial for operating the switches S, P, which take the place of, and are connected to the line in the same manner as switches S and P, respectively of li 1. The switches S, l, are normally closed, and the dial (Z occupies the position illustrated. Th s dial is provided with a plurality of teeth t which are adapted to co-operate with the primary switch P in n'oducingr the short. interruptions oti current over line limb andv with an elongated tooth which is adapted to co-operate with switch S in order to produce a prolonged interruption of current in line limb $2. In operation, the dial (Z is moved. in the direction of the arrow until. the desired number oi? teeth 25 have passed beyond the end of the switch P. During; this IPzOYGHlODlF; the elongated tooth it also passes the end of the switch S. \Vhen the dial released after such movement, it is restored to normal by the retractile spring 3 and during this movement, the several teeth 2?, which have passed beyond switch P, open the switch P a corresponding num ber ot times. and this is followed by tooth t engaging: switch S and opening; it. reason of" the relative lengths ot the teeth t and t short interruptions occur by the operation ot switch P and a prolonged interruption by the operation of switch S.

l Vhile I have illust 'ated switches A, A." and A? as being); individual to the line of a calling subscriber, I do not wish to be limited to such individual relation. as it is obvious that my invention is applicable to structures in which corresponding; switches are common to a number of lines; or are but temporarily asociated with any line desired. The several ground connections indicated are to be understood as connections to the return side of the battery or the otlice return. with the exception of the earth connection g which is a connection to earth or to a'return conductor at the substation. While I have indicated certain of the magnets or relays as being; operated by interruptcrs l and 1 it is to be understood that the vibrall y tory action of the magnets thus controlled may be secured in any desired manner when circuit is closed. While I have indicated a particular busy back arrangement-at I and U, it is to be understood that any desired arrangement maybe employed for producing a chara-urteristicsound which may be transmitted to the substation of the calling line to indicate that the desired line is busy.

it is to be understood that any desired formof construction may be employed for securing the necessary relations between the wiper to A. E. Keith et al.,

' Wherever in the description or claims I have referred to a prelim1naryswltchi'ng operation, I mean a switching operation controlled by the initial vertical motion of any wiper shaft, orby the initial angular motion of the wiper shaft of th connector switches A A or A Vherever Iliavc referred to a primary operation of the switch, I mean an operation resulting from a short, interruption of'the line circuit. Vherever I have referred to a secondary operation of the switch, I mean an operation resulting only from a long interruption of the line circuit. \Vhcrever I have referred to a long interruption)? Imean an interruption of the low resistance circuit at the substation, of sufiicient duration to allow the armatures of relays SR, SR, SR or SR to be retracted; The phrase short interrupt-ion means an interruption of the same circuit, of insufiicient durationto allow the retraction ofthe, armatures ofthese relays, but of 'suflicient duration to operate the armatures of relays PR, PR, PR? or PR"; I have. also used the terms ,current variations and variations of current in the claims in a broad sense to include changes of current to Zero. valve as well as to other y'alues,

It is obvious that various alterations and modifications may be made in the structures indicated without departing, from the spirit of my invention, and I do not wish to be limited to those structures illustrated and described. 7

What I consider new and IIOX'Ql and desire to securev by Letters Patent of the United States is r 1. A telephone exchange system comprisin g a telephone line extending from a central cities to a distant point, a source of current incircuit with said line, manually controlled means at said distant point for interrupting the circuit of the, line, other telephone lines, an electrically controlled switch'at the censwitching operation whereby an immediately I succeeding long interruption of the circuit of said line Will cause a secondary switching operation.

2. A telephone exchange system comprising a telephone line extending from a central office to a distant point, a source of current in circuit'with said line, manually controlled means at said distant point for interrupting the circuit of the line, other telephone lines, an electrically controlled switch at the central oiiice for establishing connection between said line and said other lines, active contacts for said switch constituting terminals for said line, passive contacts' for said switch constituting terminals for said other lines, restoring means for said switch, means responsive to short interruptio'nsoii the'circu-it of said linefor causing primary operation of, said switch, and means responsivewhen the circuit of said lineis initially closed at said dist-ant point for causing a preliminary switching operationwherby an immediately succeeding long interruption of the circuit of said line will cause the operation of said restoring means-. I V

3. A telephone exchange system com prising a'telephone line'extending from a centralfoffice to a. distant point, a source of currentin circuit with saidl'ine, manually controlled'means at said distant point for interrupting'the circuit of the line, other telephone lines, an electrically controlled switch at the central office for establishing connection between said line and said other lines, active contacts forsaid switch constituting terminals for said line, passive contacts. for said switchconstituting terminals for said other lines, iestoringmeans for said switch, means responsive to short inter? ruptions of the circuit" of said line for causing a primary operation of said switch, and means responsive to twosdirectly. succeeding' long interruptions of the circuit of said line for causing the operation of said restoring means.

, 4. A telephone exchange system com} prising a telephone line extending from a central ofiice to a distantpoint, a. source of current in circuitwith said line, manually controlled means at said distant point for interrupting the circuit ofthe line, other telephone lines, an electrically controlled switch having motion in two intersecting planes at the central o'l'iice for establishing connection between said line and said other lines, active contacts for said switch constii'uting terminals for said line, passive confacts for said switch constituting terminals for said other lines, restoring means for said switch, means for individual use of said switch responsive to short interruptions of the circuit of said line for causing a primary operation of said switch, and means responsive after connect-ion is established with a desired line whereby a long interruption of the circuit of said line will cause a secondary operation of said switch.

5 A telephone exchange system comprising a telephone line extending from a central oilice to adistant point, a source of current in circuit with said line, manually controlled means at said distant point for interrupting the circuit of the line, other telephone lines, an electrically controlled switch having motion in two intersecting planes at the central office for establishing connection between said line and said other lines, active contacts for said switch constituting terminals for said line, passive contacts for said switch constituting terminals for said other lines, restoring means torsaid switch, means responsive to short interruptions of the circuit of said line for causing a primary operation of said switch, and means for individual use of said switch responsive after connection is established with a desired line whereby a long interruption of the circuit of said line will cause the operation of said restoring means.

6. A telephone exchange system comprising a telephone line extending from a central ofiice to a distant point, a source of current in. circuit with said line, manually controlled means at said distant point for interrupting the circuit of the line, other telephone lines, an electrically controlled switch at the central oflice for establishing connection between said line and said other lines, active contacts for said switch. constituting terminals for said line, passive con tacts for said switch constituting terminals for said other lines restoring means for said switch, means responsive to short interruptions of the circuit of said line for bringing said active contacts into association with any desired passive contacts, and means responsive when the circuit of said line is initially closed at said distant point for causing a preliminary switching operation whereby an immediately succeeding long interruption of the circuit of said line will cause a secondary switching operation.

7. A telephone exchange system comprising a telephone line extending from a central o'llice to a distant point, a source of current in circuit With said line, manually controlled means at said distant point for interrupting the circuit of the line, other telephone lines, an electrically controlled switch at the central ollice for establishing connection between said line and said other lines, active contacts "for said switch constituting terminals for said line, passive contacts for said switch constituting ter n'iinals for said other lines, restoring means for said switch, means responsive to short interruptions of the circuit of said line for bringing said active contacts into association with any desired passive contacts, and means responsive when the circuit of said line is initially closed at said distant point for causing a preliminary switching operation whereby an imn'iediately succeeding long interruption of the circuit of said line will cause the operation of said restoring means.

8. A. telephone ez-zchange system comprising a telephone line extending from a central oillce to a distant point, a source of current in circuit with said line, manually controlled means at said distant point for interrui'iting the circuit of the line, other telephone lines, an electrically controlled switch at the central oliice for estal'ilishing connection between said line and said other lines, active contacts for said switch constituting terminals for said line, passive contacts for said switch constituting terminals for said other lines, restoring means for said switch, means responsive to short interriqations of the circuit of said line for bringing said active contacts into association with any desired passive contacts, and means responsive to two directly succeeding long interruptions of: the circuit of said line for causing the operation of said restoring means.

9. A telephone exchange system compris ing a telephone line extending from a central Oll lCG to a distant point, a source of current in circuit with said line, manually controlled means at said distant point for ii'iterrupting the circuit of the line, other telephone lines, an electrically controlled switch at the central oiiice for establishing connection between said line and said other lines, active contacts for said switch constituting terminals for said line, passive contacts for said switch constituting terminals for said other lines, restoring means for said switch, means responsive to short interruptions of the circuit of said line for bringing said active contacts into association with any desired passive contacts, and means responsive after connection is established with a desired line whereby a long interruption of the circuit of said line will cause a secondary operation of said switch.

10. A telephone exchange system comprising a telephone line extending from a central oilice toa distant point, a source of current in circuit with saidiline, manuall controlled means at said distant point for interrupting the circuit of the line, other telephone lines, an electrically controlled switch at the central oliice for establishing conncption between said line and said other lines, actire contacts for said switch c0nstituting terminals for said line, passive contacts for said switch constituting terminals :l or saidother lines, restoring means :l'orsaid switch, means responsive to short interruptions of the circuit 0:1 said line for bringing said, active contacts into association with any desired passive contacts, and means responsive after connection is established with a desired line whereby a long interri'iption of the circuit of said line will cause the operation of said restoring means.

11. A telephone exchange system comprising a telephone line extending from a central otlice to a distant point, a source of current in circuit with said line, manually controlled means at said distant point for interrupting the circuit of the line, other telephone lines, an electrically controlled switch at the central office for establishing connection between said line and said other lines, active contacts for said switch constituting terminals for said line, passive contacts for said switch constituting terminals for said other lines, restoring means for, said switch, controlling means for said switch responsive to short interruptions of the circuit of said line, selecting means for said switch normally responsive to said control ling means whereby said active contacts are brought into relation with any group vof passive contacts, engaging means for said switch whereby said active contacts are brought into engagement with said passive contacts, 1neans responsive to a long interruption directly succeeding a short interruption of the circuit of said line for causing a secondary operation of said switch.

12. A telephone exchange system com prising a telephone line extending from a .central office to a distant point, a source of current in circuit with said line, manually controlled means at said distant vpoint for interrupting the circuit of the line, other atele hone lines, an electrically controlled switch at, the central office for establishing connection between said line and said otherlines, active contacts for said switch constituting terminals for said line, passive contacts for said switch constituting terminals for said other lines restoring means for said switch, controlling means for said switch responsive to short interruptions of the circuit of said line, selecting means lfOl said switch normally responsive to said controlling means whereby said active contacts are broi'ight into relation with any group of passivecontacts, engaging means for said sponsive .to said controlling (means 4 switch at-the rentra'l office for establishing connection between said line and said other. lines, active contacts for said switch constituting terminals for said line, passive contacts for said switch constituting terminals for said other lines, restoring means for said switch, controlling means for said switch responsive to short interruptions of the circuit of said line, switch normally responsive to said controlling brought into relation with any group of passive contacts, engaging means for said switch whereby said active contacts are brought into engagement with said passive terruption directly succeedinga short interruption of the circuit of said line for bringing said engaging means under control of said controlling means. v

14. A telephone exchange system comprising a telephoneline extending from a central office to a distant point, a source of current in circuit with said line, manually controlled means at said distant point for selecting means for saidmeans whereby said active contacts are? contacts, and means responsive to a long ininterrupting the circuit of the line, other telephone lines, an electrically controlled switch at the central ofiice for establishing connection between said line and said other lines, active contacts for said switch constituting terminals for said line, passive contacts for said switch constituting terminals for said other lines, restoring JIIQZLDS for said switch, controlling means for said switch responsive to short inter- ;ruptions ,ot the circuit of said line, selecting means for said switch normally remeans whereby said active contacts are brought into relalation withany group of passive contacts, iengaging means for said switch whereby said active contacts are brought .into engagement with said passive contacts, and means responsive to a long interruption directly succeeding a short interruption of the circuitof-said line for rendering said selecting means unresponsive to said controlling means land for bringing said engaging means under control of said controlling 15. A telephone exchange system comprising a telephone line extending from a central oiiice to a distant point, a source of current in circuit with said line, manually controlled means at said distant point for inter- .rupting the circuit of the line, other telephone lines. an electrically controlled switch at the central ofiice for establishing connection between said line and said other lines, active contacts for said switch constituting terminals for said line, passive contacts for said switch constituting terminals for said other lines, restoring means for said switch, controlling means for said switch responsive to short interruptions of the circuit of said line, selecting means for said switch normally responsive to said controlling means whereby said active contacts are brought into relation with any group of passive contacts, engaging means ror said switch whereby said active contacts are brought into engagement with said passive contacts, means responsive to a long interruption directly succeeding a short interruption of the circuit of said line for rendering said selecting means unresponsive to said controlling means and for bringing said engaging means under control of said controlling means, and means responsive to a long interruption directly succeeding a short interruption of the circuit of said line for rendering said engaging means unresponsive to said controlling means.

16. A telephone exchange system comprising a telephone line extending from a central oflice to a distant point, a source of cur rent in circuit with said line, manually controlled means at said distant point for interrupting the circuit of the line, other telephone lines, an electrically controlied switch at the central oiiice having motion in one plane to select groups and motion in another plane to select lines in the group for establishing connection between said line and said other lines, active contacts for said switch constituting terminals for said line, passive contacts for said switch constituting terminals for said other lines, restoring means for said switch, controlling means for said switch responsive to short interruptions of the circuit of said line, selecting means for said switch normally responsive to said controlling means whereby said active contacts are brought into relation with any group of passive contacts, engaging means for said switch whereby said active con tacts are brought into engagement with said passive contacts, means responsive to a long interruption directly succeeding a short interruptionof the circuit of said line for rendering same selecting means unresponsive to said controlling means and for causing an automatic operation of said engaging means, and release means including a slow acting relay individual to the switch for releasing said switch,

17. A telephone exchange system comprising a telephone line extending from a central oiiice to a distant point, a source of current in circuit with said line, manually controlled means at said distant point for interrupting the circuit of the line, other telephone lines, an electrically controlled switch at the central office for establishing connection between said line and said other lines, active contacts for said switch constituting terminals for said line, passive contacts for said switch constituting terminals for said other lines, restoring means for said switch, controlling means for said switch responsive to short interruptions oi the circuit of said line, selecting means for said switch normally responsive to said con trolling means whereby said active contacts are brought into relation with any group of passive contacts, engaging means for said switch whereby said active contacts are brought into engagement with said passive contacts, means responsive to a long interruption directly succeeding a short interruption of the circuit of said line for causing an automatic operation of said engaging means, and means for arresting the operation of said engaging means.

18. A telephone exchange system comprising a telephone line extending from a central otiice to a distant point, a source of current in circuit with said line, manually controlled means at said distant point for interrupting the circuit of the line, other telephone lines, an electrically controlled switch at the central ofiice for establishing connection between said line and said other lines, active contacts for said switch constituting terminals for said line, passive contacts for said switch constituting ter minals for said other lines, restoring means for said switch, means responsive to short interruptions of the circuit of said line for causing a primary operation of said switch, means responsive to a long interruption directly succeeding a short interruption of the circuit of said line for connecting the talking circuit of said line with the talking circuit of an idle other line, and means for transmitting a busy signal to the calling line it the line called is busy.

19. A telephone exchange system comprising a telephone line extending from a central oiiice to a distant point, a source of current in circuit with said line, manually controlled means at said distant point for interrupting the circuit of the line, other telephone lines, an electrically controlled switch at the central oiiice having selecting motions in two intersecting planes for estal'ilishing connection between said line and said other lines, active contacts for said switch con- Mamie trolled means :at saiddistant pointifor in stituting terminals for said line, passive contacts for said switch constituting terminals for said other lines, restoring means for said switch including a slow acting relay, means responsive to short interruptions of a the circuit of said line for causing a primary operation of said switch, and means responsive to a long interruption directly succeeding a short interruption of the circuit of said line for connecting a source of signaling current to the line limb of an idle other line.

20 A telephone exchange system comprising a telephone line extending from a central office to a distant point, a source of current in circuit with said line, manually controlled means at said distance point for interrupting the circuit of the line, other said active contacts come to rest on the passive contacts of a connected other line.

21. A telephone exchange system comprising a telephone line extending from a central oflice to a distant point, a source of current in circuit with said line, manually controlled means at said distant point for interrupting the circuit of the line, other .telephone lines, an electrically controlled switch at the central ofiice fOIBStabhS hHlg connection between said line andsaid other lines, active contacts'ifor said switch constituting terminals for said line passive contacts for said switch constituting termin als for said other lines, restoring means for said switch including a slow acting relay responsive to the opening of the line toirelease the switch, means responsive to short interruptions of the circuit of said line for caus ing a primary operationof said switch, and

means responsive to a long interruption directly succeeding a short interruption of the circuit of said line for connecting the-talk ing circuitof said line with the talking circult of an idle other line and for connecting a source of signaling current to the line limb of an idle other line.

Atelephone exchangesystem comprising a telephone line extending from a central o'liiceto a distant point, asource of .current in circuit with said line, manually conterrupting the circuit of the line, other telephone lines, an electrically controlled switch having motion in two intersecting planes at the central ofiice for establishing connection between said line and said other lines: and to automatically signal said other lines, active contacts forsaid switch constituting terminals for said line, passive contacts for said switch constituting terminals for said other lines, restoring means for said switch; means responsive to short interruptions lot the .circuit of said line for causing a primary operation of said switch, and a-controlling relay for said switch responsive only to long interruptions of the circuit of said line. 7 1

23. A telephoneexchange system comprising a telephone line extending from a central' oflice to a distant point, a source ofcurrent in circuit with said line, manually con-"" trolled means at said distant point for interrupting the circuit of the line, other telephone lines, an electrically controlled switch having motion in two intersecting planes at the central oflice for establishingconnection between said line and said other lines and for signaling said lines, active contacts for said switch constituting terminals for said line, passive contacts for said switch iconstituting terminals for said other lines, re storing means for said switch including a slow acting relay, for restoring said switch, means responsive to short interruptions of the circuit of said line forcausinga primary operation of said switch, for said switch responsive only to long interruptions of the circuit of said line, and means controlled by said relay for causing the operation of said restoring means.

24. A telephone exchange system -comprising a telephone line extending from a (tern'iinals for said :line, passive contacts for said switch constituting terminals for said other. lines, restoring means TfOlSalCl switch,

a controllingrelay for said switch responsive to short interruptions ofthe circuit of said line, a second controlling relay for said switch responsive only to long interruptions of the circuit of said line, and means con trolled by said relays forcausing theoperaation of said switch.

25. A telephone exchange system com- ,prisinga telephone line extending from a a controlling relay" central oliice to a distant point, a source of current in circuit with said line, manually controlled means at said distant point for interrupting the circuit of the line, other telephone lines, an electrically controlled switch at the central oilice for establishing connection between said line and said other lines, active contacts for said switch constituting terminals for said line, passive contacts for said switch constituting terminals tor said other lines, ringing means and busy signalling means l or said switch operative according to whether or not the passive contacts connected with are idle or busy, restoring means for said switch, a controlling relay for said switch responsive to short interruptions ot the circuit of said line, a second controlling relay for said switch responsive only to long interruptions ot' the circuit ot said line, and means controlled by said second relay for causing the operation of said restoring means.

26. A telephone exchange system comprising a telephone line extending from a central otlice to a distant point, a source of current in circuit with said line, manually controlled means at said distant point for interrupting the circuit of the line, other telephone lines, an electrically controlled switch at the central otiice for establishing connection between said line and said other lines, active contacts tor said switch constituting terminals for said line, passive contacts for said switch constituting terminals tor said other lines, ringing means and busy signalling means tor said switch operative according to whether the passive contact connected with is idle or busy, restoring means for said switch, a controlling relay for said switch responsive to short interruptions ot the circuit of said line, a second controlling relay for said switch responsive only to long interruptions of the circuit: of said line, means controlled by said relays for causing the operation of said Switch, and means controlled by said second relay for causing the operation of said restoring means.

27. A telephone exchange system comprising a plurality of telephone lines extending from subscribers stations, automatic switch mechanism including selectors and connectors for interconnecting calling and called lines for conversation operated by se ries of interruptions of current in the calling line circuit, each series comprising short interruptions followed by a long interruption, means under the control of a calling subscriber for producing said long and short interruptions, and automatic signalling means for signalling called idle stations.

28. A telephone exchange systenrconr prising a plurality of subscribers lines, interconnectin switch mechanism including a selector and a connector for uniting said lines for conversation, a control circuit therefor, and means for operating said mechanism in response to series of interruptions o i current in said control circuit, each series comprisin short interruptions and a single long interruption, and automatic ringing means and busy signalling means for said connector.

29. A telephone exchange system comprising a plurality of sul'iscribers lines, interconnecting switch mechanism including a selector and a connector for uniting said lines for conversation, a control circuit therefor, means tor operating said lllOUl'lZlTllSlH by series 0t interruptions of current in said control circuit; in establishing the conversational circuits, each series comprising short interruptions and a single long interruption, automatic ringing means and busy signalling means for said connector operative according to the idle or busy condition of the called line, and means for restoring said mechanism to normal upon an interruption of current in said control circuit.

30. A telephone exchange system coinprising a plurality o'l'f subscribers lines, interconnecting switch mechanism including a selector and a connector having motion in intersecting planes for uniting said lines for conversation, a control circuit therefor, automatic ringing means and busy signalling means for said connector operative to signal the called subscriber or for advising the calling subscriber that the called line is busy, and means for operating said mechanism by series of interruptions of current in said control circuit to establish the conversational circuits, each series comprising short interruptions and a single long interruption, and means at the substations of said lines for causing said interruptions.

31. A telephone exchange system comprising a plurality of subscribers lines, interconnecting switch mechanism including a selector and a connector having motion in two different planes for uniting said lines for conversation, a control circuit there't'or, busy signalling means for said connector tor connection with a calling line, means for operating said mechanism by series of interruptions of current in said control circuit to establish the conversational circuits, each series comprising short interruptions and a single long interruption, and means for restoring said mechanism to normal by a following long interruption or": current in said control circuit.

32. A telephone exchange system comprising a plurality of telephone lines extending from subscribers stations, automatic switch mechanism including a selector and a connector having motion in one plane to select groups and in another plane to connect with lines in the groups for inin one direction to select groups of lines andmotion in another direction to select lines in the; groups for interconnecting calling and called lines for conversation, and means under the control of the calli subscriber for opera-ting said mechanism toestablish conversational circuits, by series of inter rupcions of current in the cal-ling line, each series com-prising short interruptions and a single long interruption, automatic signalline means for the mechanism for signalling called lines, and a slow acting relay individual to said switch mechanism for controlling the release of the same.

34. A telephoneexch-ange system comprising a plurality of telephone lines extending from substations, automatic switch mechanism having one motion to select groups and a second motion toselect lines in the group for interconnecting calling and called lines for conversation, means under the control of the callingsubscriber for operating said mechanism to establish conversational circuits by series of interruptions V of current in the calling line, each series comprising short interruptions and a single long interruption, automatic intermittent rii'iging means for said mechanism for signailing the called subscribers, and means for restoring said mechanism to normal by a following long interruption of current in said line. 7

35, A telephone exchange system comprising; a subscribers station having a transmitter, receiver, call-bell, and call transmitting device, a two-conductor circuit extending from said station, a plurality of interconnecting link-circuits, other sub scribers lines, associated automatic step-bystep switch mechanism including a two motion selector and a two motion connector for selectively extending the two-conductor circuit tl'irough said link-circuits to said other sul'ascribers lines, means for advancing and releasing said mechanism by variations of current transmitted over said two-conductor circuit, means whereby conversation may be held. over said circuit, and means for intermittently actuating; said call-be l by current over said circuit, and means for preventing connection with the called line to establish convcr and then in another direction to a desired to operate said call bell isbusy. v

36. A telephone exchange system com prising asubscribers station having a transmitter, receiver, callbell, and call transmitting device, a two-conductor circuit extending from said station, interconnecting link-circuits, other subscribers lines, automatic step-b-y-stepswitch mechanism for selectively extending said two-conductor circuit through said linl'r-circuits to said other subscribers lines, a central source of if saidcalled line current, means for advancing and releasi r a said mechanism by variations in said two conductor circuit of current derived from said source, means for energizing said transmitter over said circuit from said source, and means for actuatingsaid callell by current over said circuit.

37.. A telephone exchange system comprising a two-conductor circuit, associated auto matic step-by-step switch mechanism includ ing a connector having Waiting contacts di vided" into groups and a co-operating moving contact, means responsive to variations of current transmitted over said circuit to advance said: moving contact in one direction to a desired group of Waiting contacts and then in another direction to a desired contact in that group, a slow acting relay for changing the direction of travel of said myi-ng contact, and a slow acting relay individual to said connector switch for restoring the same tonormal.

38. A telephone exchange system com-prisinga two-conductor circuit, associated automatic step-by-step switch mechanism including a connector having waiting contacts db vided into groups and a co-operating movcontact, means responsive to variations of current transmitted over said circuit to advance said moving contact in one direction to a desired group of Waiting contactscontact in that group, a slow acting relay individiual to said connector for effecting the change in direction oi movement of said movable contact, and means responsive to a change in the current condition in said circuit to bring said moving contact to its nor mal position.

39. telephone exhange system compris ing a two-conductor circuit, associated automatic switch mechanism having Waiting contacts divided into groups and a co-operatilng movin 7 contact, means outside 01" said mechanism for rendering some of said waiti'ng contacts busy, means for advancing 

